Electrochemical recording



black in color.

United States Patent ELECTROCHEMICAL RECORDING .Harold R. Dalton, Jenkintown,,Pa., assignor to Timefax Corporation, New York, N.Y., a corporation of New York No Drawing. Filed Sept. 30,1958, Ser. No. 764,295 6 Claims.- (Cl. 204-2) This invention relates to the art of recording electric signals, and more especially it relates to recording cur rents by electrochemical means.

A principal object of the invention is to provide an "ice for this purpose is the diamide of thiooxalic acid. When such a blank is used with a recording anode of copper, there is produced a dark brown mark in response to current flow in the blank. However, with this material the unrecorded surface of the paper is a yellowish red, the color of the diamide of thio-oxalic acid, which of course, greatly reduces the contrast or readability of the recordings. In an effort to solve that difficulty it has been proposed to employ, as the mark producing chemical, pyrocatechol. When such a catechol paper is acted upon by an iron metal recording anode, thereisproduceda dark blue-black mark. However, such a. paper has a tendency to discolor when exposed to light or air.

In order to reduce this discoloration characteristic, it was heretofore considered necessary to have present an antioxidant or reducing agent. However, such materials are not very effective and some undesired discoloration alrecording blank having one or more of the usual elec trolytic conductor salts and mixed with a novel color forming compound or agent.

In the art of marking or recording by means of applied electric voltages, for example in the art of facsimile recording on electrochemical blanks, usually of paper,

the recording mark is made by locating the blank while in suitably moistened condition between a pair of electrodes across which the signal voltages are impressed. Usually both electrodes are in contact with the blank so as to produce complete conductive path through the thickness of the blank. The electrodes, for example,

may be in the form of intersecting knife edges, one' of which for example may be 'a helical knife edge on a namely the anode which may be'in the form of a pointed stylus. 'As a result of this ionic action at the anode, foreign ions are introduced into the recording blank, i.e.-metallic ions from the anode itself enter the recording blank, which ions then react with the color forming compound contained therein to produce a distinctive colored mark in the blank. Thus if pyrocatechol (1,2 benzenediol) was present in the blank as a color forming compound along with an electrolytic salt such as potassium nitrate and a stylus of iron was used as the anode, an impressed voltage would liberate metallic ions from the stylus a which would then react with the pyrocatechol to form a metallic complex with the pyrocatechol which is blue- Other color forming compounds will react similarly with metallic ions from the stylus, the

color of the complex being somewhat dependent upon the type of metal used as the anode.

The prior art discloses different kinds of blanks for such use, consisting of paper suitably impregnated with marking operations can be eifected in a variety of ways. well known in the art. In accordance with the present invention, preferably the marking action involves the "discharge of metallic ions from one of 'the' electrodes,

appropriate chemicals. One of the chemicals known ways occurs.

-While many other formsof electrochemical recording papers have been proposed, they all possess some objectionable features such as bleeding of the recording mark beyond the desired elemental area; a normal colorecl surface is required in the blank; high operating current is required for a given marking effect; instability towards air, heat or light; and some blanks even require a separate color developing operation after the record mark has been made.

'It is, therefore, another principal object of this invention, to provide an electrochemical recording. blan which overcomes the above noted objections.

In general, the invention provides an electrochemical blank or sheet which is arranged to be acted upon by an electricallyenergized stylus which forms an anode, so that the current erodes the anode and produces a con -centration of metallic ions at the point of the stylus.

These metallic ions then react with the compounds of the electrolyte plus the special color-forming ingredient contained in the recording medium in the blank to produce a mark in the form of a metalloorganic complex that is permanent and relatively free from bleeding and which does not require subsequent development even with high speed recordings.

In accordance with the invention, the blank is in the form of a paper sheet relatively free from metallic impurities, such as conventionally used in making electro chemical recording blanks, or it may be of cloth or similar material which can be impregnated with chemicals, and thenmoistened during recording. In thecase of paper, it preferably includes any of the well known ingredients for imparting substantial wet strength thereto, such for example as urea-formaldehyde resins, melamineformaldehyde resins, polyvinyl resin lattices, and the like. The wet strength paper or cloth sheet is then wetted, impregnated or saturated on one or both surfaces with any of the well known electrolytic salts such as are used in the marking of electrolytic facsimile recording blanks, together with the color-forming agent or agents to be described. Usually the electrolytic salt is lithium, sodium, or potassium chloride, nitrate, or sulfate. Since these electrolytic salts are well known in the art, detailed listing thereof is not considered necessary herein. Likewise, as is well known, auxiliary chemicals may be utilized to control the pH, solubility of the color forming compound, paper softness, etc. Typical of these known auxiliary chemicals are acids or acid salts such as oxalic acid and sodium bisulfate, etc., and alkali or alkaline salts such as sodium hydroxide, potassium oxalate, etc., humectants such as ethylene glycol, diethylene glycol, glycerine, etc. Regardless of which particular electrolytic salt and auxiliary ingredient are used, provided uniform solubility exists without chemical reaction,

I have found that improved results are obtained if there is added to the electrolytic salt solution a special color- ,formingagent of a quinoline derivative having the following chemical structure:

wherein: x is halogen or hydrogen or hydroxyl group; y is halogen, or hydrogen or hydroxyl group or sulfonic acid group; z is a hydroxyl group. The above noted color-formingagent should be present to the extent of about 1 percent to 30 percent based on the solids in the salt solution. It is desirable that the color-forming agent be in itself colorless so as to produce a colorless recording paper. Also the color-forming ingredient and 'the solution should be substantially entirely free from nitrite ions, since the presence of such ions causes an undesirable breakdown of the quinoline and tends to impart to the normally whitish background color of the blank, an undesirable brownish color.

Without limiting the invention, the following is an actual example of typical proportions that may be used to saturate a wet strength saturating paper weighing approximately 25 pounds (24" x 36"--500 sheets), the paper having a thickness of approximately 0.0025":

Grams Water 100.0 Potassium nitra 10.0 (Dxalic acid 1.0 Ethylene glycol 3.0 Color forming agent 1.0-5.0

simile signal currents, the negative terminal of which source may be grounded. The electrolytic sheet can be supported on a grounded metal base or drum so that by producing relative movement between the recording stylus and the support, the surface of the sheet can be scanned in successive elemental areas. In one particular circuit the stylus anode had its recording tip of an iron or iron alloy. In one particular circuit that was found to produce the desired results, the signal source produced at the stylus a positive voltage of 250 volts with respect to the support, resulting in a current flow of approximately 100 milliamperes through the electrolytic blank treated as hereinabove described, to produce a record or mark on the said blank. This mark is produced as a result of metallic ions from the stylus anode reacting with the above noted color forming ingredient to form a quite insoluble, internal, covalent, complex polymer compound or metallo-organic complex. The

,expression quinoline derivative. as referred to herein,

means the normal as well as the iso form of such derivative. By the expression wetted as used herein, is meant saturating or applying a controlled predetermined amount of solution to one or both surfaces of the blank.

This application is a continuation-in-part of application Serial No. 542,752, filed October 25, 1955, now abandoned, and of application Serial No. 618,119, filed October 24, 1956, now abandoned.

What is claimed is:

l. Electrosensitive sheet material especially prepared for electrolytic marking inffresponse to applied electric currents and being in the form of a porous web of whitish background wetted with a conductive normally colorless electrolytic marking salt solution such as used in facsimile recording and which has added thereto a color forming agent in the form of a quinoline derivative and which reacts with ions from a recording electrode to produce a colored mark, said agent having the following chemical structure v where "x is chosen from the group consisting of halogen,

hydrogen, hydroxyl, y is chosen from the group consisting of halogen, hydrogen, hydroxyl-group, sulfonic acid-group, and z is a'hydroxyl group, said'solution being substantially entirely free from nitrite ions which tend to react with the quinoline to impart an undesirable which reacts with ions from a recording electrode to produce a colored mark, said agent having the following chemical structure 11 where x is chosen from the group consisting of halogen, hydrogen, hydroxyl, y is chosen from the group consisting of halogen, hydrogen, hydroxyl-group, sulfonic acid-group, and z is a hydroxyl group, said solution being substantially entirely free from nitrite ions which tend to react with the quinoline to impart an undesirable brownish color to said background.

3'. An electrochemical material for impregnating a recording blank having a whitish background for electrolytic recording thereon by means of metal ions released from a recording electrode, said material consisting essentially of a normally colorless conductive electrolytic salt solution which has added thereto a color forming agent of ..a quinoline derivative and which reacts with metallic ions released from a recording electrode to produce a'colored mark, said agent having the follow ing chemical structure 1 where x is chosen from the group consisting of halogen, hydrogen, hydroxyl, y is chosen from the group consisting of halogen, hydrogen, hydroxyl-group, sulfonicacid-group, and z is a hydroxyl group, said solution being substantially entirely free from nitrite ions which tend to react with the quinoline to impart an undesirable brownish color to said background.

4. An electrochemical material for impregnating a recording blank having a whitish background for electrolytic recording thereon by means of metal ions released from a recording electrode, said material consisting essentially of a normally colorless conductive electrolytic salt solution which has added thereto a color forming agent of a quinoline derivative and which reacts with metallic ions released from a recording electrode to produce a colored mark, said agent having the following chemical structure where x is chosen from the group consisting of halogen, hydrogen, hydroxyl, y is chosen from the group consisting of halogen, hydrogen, hydroxyl-group, sulfonic acid-group, and z is a hydroxyl group, said solution being substantially entirely free from nitrite ions which tend to react with the quinoline to impart an undesirable brownish color to said background.

5. An electrochemical material for impregnating a recording blank having a whitish background for electrolytic recording thereon by means of metal ions released from a recording electrode, said material consisting essentially of a normally colorless conductive electrolytic salt solution which has added thereto a colorless color forming agent of a quinoline derivative and which reacts with metallic ions released from a recording electrode to produce a colored mark, said agent having the property of being free irom discoloration in air at normal operating temperatures but which discolors to produce a contrasting mark when subjected to said ions, said solution being substantially entirely free from nitrite ions which tend to react with the quinoline to impart an undesirable brownish color to said background.

6. The method of preparing an electrolytic recording blank in the form of a porous web having a whitish background which comprises, impregnating the web with a solution consisting essentially of an electrolytic salt which is normally colorless and conductive and is mixed with a colorless color-forming agent of a quinoline derivative to form an impregnating solution which is sub stantially entirely tree from nitrite ions which tend to react with the quinoline to produce an undesirable brownish color in said background when said web is impregnated therewith, said solution having the property of responding to metallic ions released from a recording electrode to produce a corresponding colored mark on the blank.

References Cited in the file of this patent UNITED STATES PATENTS 2,038,486 Glas Apr. 21, 1936' 2,419,296 Solomon Apr. 22, 1941 2,663,656 Miller et a1. Dec. 22, 1953 2,686,858 Kohn et a1. Aug. 17, 

1. ELECTROSENSITIVE SHEET MATERIAL ESPECIALLY PREPARED FOR ELECTROLYTIC MARKING IN RESPONSE TO APPLIED ELECTRIC CURRENTS AND BEING IN THE FORM OF A POROUS WEB OF WHITISH BACKGROUND WETTED WITH A CONDUCTIVE NORMALLY COLORLESS ELECTROLYTIC MARKING SALT SOLUTION SUCH AS USED IN FACSIMILE RECORDING AND WHICH HAS ADDED THERETO A COLOR FORMING AGENT IN THE FORM OF A QUINOLINE DERIVATIVE AND WHICH REACTS WITH IONS FROM A RECORDING ELECTRODE TO PRODUCE A COLORED MARK, SAID AGENT HAVING THE FOLLOWING CHEMICAL STRUCTURE 